1. Field of the Invention
The present invention relates to a portable liquid level detector, and method for detecting the level of a liquid in a container.
2. Description of the Related Art
In some semiconductor processes, liquid supply is necessary. For example, chemical slurries or the like used in chemical mechanical polish (CMP) processes require liquid provision. However, sometimes the container used to contain liquid is nontransparent, so that process engineer doesn't know how much liquid remains in the container. In this case, the process engineers sometimes estimate how much liquid remains in the container by knocking the container and listening to the corresponding sound from the container. But sometimes the process engineer's estimation is wrong, in which case the liquid supply may be interrupted, ruining semiconductor products. Another way to know how much liquid remains in the container is to use a flow measuring system to detect the weight of the container with liquid. However, the flow measuring system is not cheap. So, if a flow measuring system must be provided with every process that needs liquid supply, the cost is high.